Disc-brake brakeshoe

ABSTRACT

A disc-brake brakeshoe has a backing plate carrying a brake lining. This plate has a portion bent toward the disc along a bend line which is removed or offset from the center of the shoe and is generally directed toward the center of a brake disc. When the brakeshoe is greatly worn, the trailing, inwardly bent edge contacts and scrapes against the brake disc, thereby creating an audible signal for the driver, without imparting braking characteristics since the major portion of the lining remains effective at least until the operator of the vehicle has recognized the danger and had an opportunity to replace the brakeshoe or have the backing plate relined.

United States Patent lnwntor Hans Joachim Anders Frankfurt am Main.Germany Appl Nu 782,849 Filed Dec. 11,1968 Patented Mar. 2, 1971Assigncc Alfred Teves G. m.b.11.

Frankfurt am Main, Germany Priority Dec. 15, 1967 Germany P 16 25 831.4

DISK-BRAKE BRAKESHOE 5 Claims, 5 Drawing Figs.

US. Cl 188/73.l; 188/250 Int. Cl Fl6d 66/02 Field of Search 188/1 (A),

plication Tenes Primary Examiner-George E. A. Halvosa Attorney-Karl F.Ross ABSTRACT: A disk-brake brakeshow has a backing plate carrying abrake lining. This plate has a portion bent toward the disk along a bendline which is removed or offset from the center of the shoe and isgenerally directed toward the center of a brake disk. When the brakeshoeis greatly worn, the trailing, inwardly bent edge contacts and scrapesagainst the brake disk, thereby creating an audible signal for thedriver, without imparting braking characteristics since the majorportion of the lining remains effective at least until the operator ofthe vehicle has recognized the danger and had an opportunity to replacethe brakeshoe or have the backing plate relined.

PATENTEUHAR 2197+ 3566895 SHEET 2 [IF 2 Hans J. Anders INVENTOR.

(Look 03 5i A ttorney DISK-BRAKE BRAKESHOE My present invention relatesto disc-brake brakeshoesand, more particularly, to a brakeshoe havingmeans for preventing brake squealing and noise.

in my commonly assigned copending application Ser. No. 672,757, filed 12Dec. I966 now abandoned, and commonly assigned US. Pat. No. 3,409,106,issued to Ernst Meier and Hermann Seip on Nov. 1968, there are describesystems for reducing the noise produced by disc brakes upon theapplication of brake pressure.

In these applications it is pointed out that, when the brake pistonbears centrally (i.e. along its axis) upon the backing plate of abrakeshoe, the nonuniform wear of the brake lining due to higher surfacespeeds at greater distances from the center of rotation of the discresults in a canting of the brakeshoe which is associated with thegeneration of brake noise during the application of the disc brake. v

A disc-brake system of this general type comprises a fixed yoke orhousing whose lobes are disposed on opposite sides of a brake disc whichis rotatably secured to the axle or wheel of the automotive vehicle; thelobes are connected by a bridge piece.

It has been noted in the commonly assigned, copending application Ser.No. 687,043, filed 30 Nov. 1967, by J.R. Bot terill and entitledAnti-noise Disc Brake," now US. Pat. No. 3,460,652 that it isunnecessary to wait for a brake-lining wear of about l0-l5 percent, ashas been the case when intervening plates having a thickness of about 1mm. have been introduced to render the contact'between the piston andthe brakeshoe off center, or to reduce the-thickness of the brake liningif an intervening plate is to be used from the beginning, when thedisc-type brake has a piston whose annular end confronting the brakeshoeis stepped (i .,e. provided with at least three steps) to afford alimited zone of contact with the backing plate of the shoe.

This latter application further discloses that the hydraulic disc brake,which does not require an intermediate plate, can effectively beprovided with a wheel-brake piston of cylindrical cupshapedconfiguration which opens in the direction of the backing plate of thebrakesho'e. The piston thus has an annular rim juxtaposed with thebacking plate of the brakeshoe and forming the contact surface by whichthe piston applies force to the shoe. To minimize brake noises andespecially squealing without changing the usable thickness of the brakelining and without using an intermediate plate, the piston is providedwith a plurality of axially staggered but planar steps, i.e. at leastthree axially staggered zones, which lie in planes parallel to thebacking plate of the disc but are offset one from the other by cuttingaway the annular contact end of the piston. Advantageously, the thirdstephas a height less than the first step and of approximately 0.1 mm.The third or additionai step is closest to the backing plate and iscompressible.

BACKGROUND OF THE INVENTION These prior-art devices do indeed make for adisc brake which is virtually squeal-free, yet they are relativelyexpensive to produce. Furthermore, they provide no means of warning thedriver when his brakeshoes are worn dangerously low, and therefore needreplacement.

OBJECTS or The INVENTION it is the principal object of my invention toprovide a bralteshoe which has the antisqueal properties of the aabovementioned devices, while being relatively inexpensive tomanufacture.

A further object of my invention is to provide such a brakeshoe thatwarns the driver when his brakes need servicing i.e., when thebrakeshoes are worn dangerously low, without greatly impairing thebraking characteristics of the vehicle.

SUMMARY or THE INVENTION I do this through the surprisingly simpleexpedient of providing a brakeshoe with a backing plate that has aportion which is bent toward the disc and away from the piston along arectilinear bend or ridge line. In this way the off center support ofthe brakeshoe is ensured without major redesigning of the brake piston.

In addition the forwardly bent edge of this backing plate, on pronouncedbrakeshoe wear, will rub or scrape the disc giving rise to a simpleaudible signal readily recognizable as indicating metal-to-metal contactand the erosion of the intervening brake lining. Upon onset of thissignaling the driver can safely continue driving, since, in contrast tonormal brakeshoes, he still has the major part of its brake lining leftin contact with the disc. At his leisure in a reasonably long time afterthe start of the signal the operator can have the brakeshoes replaced.

According to a further feature of my invention, this bend line iseccentrically located onthe backing plate and is directed generallytoward the center of the disc. This permits most effective transfer offorce from the piston to the disc while preventing to a maximum extentthe squeal hitherto characteristic of disc brakes omitting theimprovements of the aforementioned application and patent.

BRIEF DESCRIPTION OF THE FIGURES These and other features, objects, andadvantages of my invention will be described in the following, withreference to the drawing in which:

FIG. 1 is a partial sectional view through a disc brake equipped withthe brakeshoe according to my invention;

H68. 2 and 3 are views similarto FIG. ll showing the brake lining inadvancing states of wear;

H0. 41 is a view taken along line IV-IV of FIG. 1; and

FIG. 5 is a view similar to FIG. 4 showing a further embodiment of myinvention.

SPECIFIC DESCRIPTION FIG. I shows a disc brake as described in thecommonly assigned application Ser. No. 700,515 filed on 25 Jan. 1968 byJuan Belart and entitled Adjusting Device for Disc Brake, now US. Pat.No. 3,498,423. This brake has a brake disc 1 which is engaged by abrakeshoe comprising a brake lining 2 mounted on a backing plate 3. Apiston 4, axially displaceable in a cylinder 5 which is pressurizablethrough a port 6, urges the lining 2 against a braking surface 7 of thedisc I.

The backing plate 3 has a straight ridge or bend line 8 directed at thecenter A of the disc I seen in FIG. 4, this plate being bounded by atrailing edge 3a and a leading edge 312. An alternate backing plate 3has a bend line 8' which lies on a chord of the disc (FIG. 5). Ineithercase the ridge line 8 or 8' lies within the axial projection 9 of theoutline of the piston 4 on the disc, thus within the path of the pistonand is offset toward trailing edge 3a; from a centerline w of thebrakeshoe which intersects the axis of the piston 4.

FIG. 2 shows the brake lining 2 worn. to the point where the trailingedge 3a contacts the disc I and thereby creates an audible signal forthe driver.

In FIG. 3 a fully worn out brakeshoe is shown. In this terminal positionboth the trailing edge 3a and the leading edge 3b contact the disc I sothat only on defamation of the plate 3 can the residue of lining 2effectively contact the disc i. Ridge 8, separating the two plateportions which diverge at an obtuse angle toward the disc and arebounded by edges 3a and 312, respectively, points toward the piston 4bearing upon the plate 3 There is a reasonably long period of completelysafe braking between the conditions shown in FIGS. 2 and 3, during whichample time exists to have the old brakeshoes replaced. if, for somereason, the audible signal is ignored, the braking characteristics ofthe vehicle will be slowly changed, requiring more pressure on the brakepedal, to act as a further warning for the driver. In no case is there asudden failure of braking due to a total lack of brake lining on thebrakeshoe.

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theinvention except as limited by the appended claims.

lclaim:

1. in a disc brake having a piston axially displaceable toward a brakingsurface of a brake disc to urge a brakeshoe thereagainst, the brakeshoecomprising a metallic backing plate engageable by said piston and abrake lining on said backing plate confronting said braking surface, theimprovement wherein said backing plate has two portions adjoining eachother at an obtuse angle along a ridge line lying in the path of saidpiston, said portions beingrespectively bounded by a leading edge and atrailing'edge; said backing plate being movable under pressure of saidpiston, upon an erosion of said brake lining at both said edges, into aterminal position in which said braking surface contacts both said edgesand a residual layer of brake lining therebetween, with said ridge linepointing toward said piston.

2. The improvement defined in claim 1 wherein said ridge line is offsetfrom the axis of said piston.

3. The improvement defined in claim 1 wherein said ridge line lies alonga radius of said disc.

4. The improvement defined in claim 1 wherein said ridge line lies alonga chord of said disc.

5. The improvement defined in claim 1 wherein said ridge line liescloser to said trailing edge than to said leading edge.

1. In a disc brake having a piston axially displaceable toward a brakingsurface of a brake disc to urge a brakeshoe thereagainst, the brakeshoecomprising a metallic backing plate engageable by said piston and abrake lining on said backing plate confronting said braking surface, theimprovement wherein said backing plate has two portions adjoining eachother at an obtuse angle along a ridge line lying in the path of saidpiston, said portions being respectively bounded by a leading edge and atrailing edge; said backing plate being movable under pressure of saidpiston, upon an erosion of said brake lining at both said edges, into aterminal position in which said braking surface contacts both said edgesand a residual layer of brake lining therebetween, with said ridge linepointing toward said piston.
 2. The improvement defined in claim 1wherein said ridge line is offset from the axis of said piston.
 3. Theimprovement defined in claim 1 wherein said ridge line lies along aradius of said disc.
 4. The improvement defined in claim 1 wherein saidridge line lies along a chord of said disc.
 5. The improvement definedin claim 1 wherein said ridge line lies closer to said trailing edgethan to said leading edge.